Federal forecasters predicted this summer's harmful algal bloom in Lake Erie could be larger than the 2014 bloom depicted here that forced the shutdown of Toledo's water system for three days.

Federal forecasters predicted this summer's harmful algal bloom in Lake Erie could be larger than the 2014 bloom depicted here that forced the shutdown of Toledo's water system for three days.(AP file photo)

CLEVELAND, Ohio - A harmful algal bloom "significantly larger" than last summer's, and potentially the third-largest on record, is likely to grow in Lake Erie's western basin this summer, federal forecasters predicted Thursday.

The bloom, which at times appears as if someone spilled pea soup into the lake, has become an annual nuisance over the past decade, that required the closing of beaches, game fish such as walleye and perch to migrate to cleaner water, and threatened drinking water.

In 2014, dangerous bacteria from the bloom forced Toledo's water system to be shut down for three days.

"This year's bloom is likely to be significantly larger than the average year, approaching some of the largest blooms on record," said forecaster Don Scavia, an aquatic ecologist at the University of Michigan.

This chart shows the mass of Lake Erie's harmful algal blooms the past 15 years. The 2017 bloom could match the third-largest bloom in 2013, according to the forecast released Thursday.Graph courtesy of NOAA

Bloom size does not necessarily correlate with its risk to public health, however. Spring rainfall, phosphorus runoff from farm fields in the Maumee River watershed, wind direction and water temperature all play a role in the size and the toxicity of the algal blooms, said Rick Stumpf, an oceanographer at the National Oceanic and Atmospheric Administration.

Heavy rainfall in May and July, totaling 25 inches since March 1, appears to have caused a large flow of algae-feeding phosphorus runoff from farm fields, Stumpf said Thursday during a conference at Ohio State University's Stone Lab on Gibraltar Island near Put-In-Bay.

An estimated 85 percent of the phosphorus entering Lake Erie from the Maumee River comes from agricultural sources.

Stumpf said, based on five different data sources, that this summer's algal bloom likely will be more than double the size of last summer's bloom, which was one of the smallest in the last decade. But it will probably fall short of the record bloom of 2015, and the second-largest in 2011, he said.

He declined to predict the potential danger of the bloom.

"We can estimate the biomass of the bloom, but we do not have the ability yet to forecast the toxicity," Stumpf said.

How far the bloom spreads out of the western basin will depend on the winds, he said. "If there's a Northeast wind, Ohio has a problem," Stumpf said. "Southwest winds, you may not see it here in Ohio. Much of the lake will be fine most of the time."

The algal blooms seldom spread as far east as Cleveland, he said. No blooms have been detected yet this summer, and are not expected to begin growing until later in the month or early in August.

This summer, for the first time, NOAA will track the algal blooms with a new weather satellite, Sentinel-3, that will beam back to Earth a more accurate picture, providing the power to detect blooms one-tenth the size of blooms previously detected, Stumpf said. A second Sentinel-3 will be launched later in the year.

Environmental groups quickly weighed-in on the forecast Thursday, issuing their own predictions of gloom for the summer.

"With a bloom of this size and scale expected, it is clear that this problem can only be addressed at the source," said Nicholas Mandros of the Ohio Environmental Council. "Toxic algae is primarily caused by agricultural runoff, and Ohio's voluntary approach simply isn't enough to curb the algae-causing pollution flowing into Lake Erie."

Mandros acknowledged that many farmers are working to curb phosphorus runoff, but more farmers need to participate to solve the problem. This requires broad scale conservation practices and only applying the amount of manure and fertilizer that is necessary.

Ohio, Michigan and Ontario have struck an agreement to reduce phosphorus runoff by 40 percent by 2025. But most environmentalists maintain the state proposals for reaching that goal will prove inadequate because they don't provide state laws limiting fertilizer and manure application.

Both of Ohio's U.S. senators reacted to the announcements, and cited the reports as evidence of the value of the Great Lakes Restoration Initiative and the federal budgets for NOAA's Sea Grant program, which funds the Stone Lab. All are on the chopping block among the Trump Administration's proposals, but should be fully funded, according to the senators.

"We need every tool at our disposal to protect the health of Lake Erie," said Sen. Sherrod Brown, a Democrat. "The millions of Ohioans who rely on the lake can't afford to lose important resources like the Great Lakes Restoration Initiative as they face the threat of algal blooms."

Sen. Rob Portman, a Republican, said: "NOAA's forecasting is critically important to help prepare for and mitigate the impacts of harmful algal blooms in Lake Erie... Although great progress has been made to reduce blooms in the Great Lakes, NOAA's prediction of a significant bloom this summer highlights the need to ensure programs like the Great Lake Restoration Initiative are fully funded so that we can continue to protect the Great Lakes."